Pain is "an unpleasant sensory and emotional experience associated with actual or potential tissue damage". Evaluation of pain in neonates is difficult due to the subjective nature of pain and the inability of neonates to verbally express pain. Surrogate measures used to describe pain in neonates include motor responses, facial expressions, cry and changes in physiologic parameters like heart rate, blood pressure, oxygen saturation and respiratory rate. Various changes have been compiled to create various scores. Validated scores for the assessment of pain include Neonatal Facial Coding System, Neonatal Infant Pain Scale or Premature Infant Pain Profile. These reactions to pain may contribute to the development of hypoxia, hypercarbia, acidosis, ventilator asynchrony, pneumothoraces, reperfusion injury and venous congestion and subsequent late intraventricular hemorrhage (IVH) or late extension of early intraventricular hemorrhage and periventricular leukomalacia. These behavioral changes may also disrupt postnatal adaptation, parent-infant bonding and feeding schedules.